HLA typings were performed on 1,082 individuals from the South Dakota colonies of the Schmiedeleut Hutterites, a Caucasian inbred isolate. This group was originally studied as part of a project assessing the relationship between HLA similarity in married couples and reproductive outcome. In the present studies, 1,082 individuals, including 852 married adults representing the reproductive population of this isolate, were characterized for five-locus HLA haplotypes based upon typings associated with the HLA-A, -B, -C, -DR, and -DQ loci. Only 48 ancestral haplotypes were observed and nine of these accounted for over 52% of the observed haplotypes. Measures of two-locus linkage disequilibria were also derived, and recombination observed through family studies. This HLA profile points out a paucity of HLA alleles and haplotypes in this population, which is characterized by both marked homogeneity and marked linkage disequilibrium among the HLA alleles that are present. Ongoing studies will further explore the notable decrease in homozygosity that has previously reported for this population, as well as patterns of allele and haplotype transmission.